| The incidence of spinal cord injury is increasing,and is the main cause of disability.However,treatments that are effective and inexpensive are lacking.Mesenchymal stem cells have a high degree of plasticity,low immunogenicity and could differentiate into neural cells after induction under specific conditions.In recent years,studies on bone marrow mesenchymal stem cells(BMSCs)have become hot spots.Therefore,we used the SD rat aneurysm clamp injury model and BMSCs as a treatment to establish a research system for the intervention of the injured spinal cord and to observe the damage of the spinal cord after the BMSCs transplantation and the protection of the demyelinating lesions.Objective:1.To study whether bone marrow mesenchymal stem cells have a protective effect on spinal cord injury;2.Determine the best bone marrow mesenchymal stem cell transplantation time;3.Further clarified that bone marrow mesenchymal stem cell transplantation has a protective effect on spinal cord injury by demyelinating lesions via inhibiting oligodendrocyte apoptosis.Methods:1.Successful model of spinal cord injury rats were randomly divided into 1-d group,7-d group and 14-d group.Bone marrow mesenchymal stem cells were transplanted into injured spinal cord on the 1st,7th and 14th day respectively.BBB exercise was used to assess the recovery of the rats.Western blot was used to detect the expressions of myelin basic protein(MBP),2',3'-Cyclic-nucleotide 3'-phosphodiesterase(CNPase)and caspase 3.Immunofluorescence was used to observe the effects of BMSCs transplantation on the oligodendrocyte apoptosis after spinal cord injury at three different time points.2.SD rats were randomly divided into sham group,SCI group and BMSCs group.After 7 days of spinal cord injury;10 ?l PBS,equal volume of PBS and BMSCs cell suspension were transplanted respectively.LFB(Luxol fast blue)staining,tannic acid staining,HE(Hematoxylin and eosin)staining and TEM were performed to observe the white matter myelinated nerve fibers.Western blot was used to detect the effect of BMSCs transplantation on the expressions of brain-derived neurotrophic factor(BDNF),Bax,Bcl-2,caspase 3,caspase 12,MBP,CNPase and cytochrome c after SCI.The expressions of CNPase-caspase 3 and MBP-cytochrome c were detected by immunofluorescence,and the apoptotic of oligodendrocytes after bone marrow mesenchymal stem cell transplantation were observed.Results:1.The BBB score of hindlimb exercise showed that the BBB exercise score of the BMSCs group was significantly higher than that of the SCI group(P<0.05).Tumid myelin sheaths and myelinated nerve fibers were decreased.The above situation was significantly improved after transplantation of BMSCs.TEM showed:degeneration were observed in the SCI group,with deformation and the appearance of many vacuoles in the myelin sheath and barely any myelination with multiple bare axons or severe disruption of myelin sheaths encompassing the injury site.There were thick,myelinated nerve fibers and a reduction in the deformation of native myelin sheaths in the BMSCs group.2.The effect of transplantation of BMSCs at different time points:the BBB score of hindlimb exercise showed that the BBB score of the 7-day group was significantly higher than that of the 1-day group and slightly higher than that of the 14-day group(P<0.05).Compared with day 1 and day 14 after spinal cord injury,the expressions of MBP and CNPase protein were highest and the expression level of caspase 3 protein was the lowest after 7 days transplantation of BMSCs.The results of immunofluorescence showed that the numbers of CNPase-caspase 3 and CNPase-TUNEL positive cells in the 7-day group were the lowest compared with the 1-day group and the 14-day group(P<0.05).3.After transplantation of BMSCs into the injured spinal cord for 7 days,immunofluorescence showed that BMSCs could partially differentiate into neurons and oligodendrocytes.After bone marrow mesenchymal stem cell transplantation,the protein expression levels of Bax,caspase 3,caspase 12 and cytochrome c were significantly lower than that in the SCI group;the expression trends of Bcl-2,MBP,BDNF,and CNPase were opposite.Immunofluorescence results showed that after transplantation of BMSCs,the numbers of MBP-caspase 9 and MBP-cytochrome c positive cells in the white matter of spinal cord were significantly lower than that in SCI group(P<0.05).Conclusion:1.BMSCs transplantation has a protective effect on spinal cord injury.2.The best time for transplantation of BMSCs into damaged spinal cord is 7 days after spinal cord injury.3.BMSCs could inhibit the apoptosis of oligodendrocytes.It may be through the transplantation of BMSCs into the damaged spinal cord to differentiate into neurons and oligodendrocytes and promote the secretion of BDNF to exert anti-apoptosis effect.Its anti-apoptotic mechanism may be related to endoplasmic reticulum stress and cytochrome c release. |
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